1. Field of the Invention
This invention generally relates to microwave cooking containers and, more particularly, to a collapsible/expandable box for popping popcorn in a microwave oven.
2. Prior Art
As is known in the art, microwave ovens radiate electromagnetic energy waves in short radio frequencies which are distributed randomly throughout the microwave oven until absorbed by a food product being heated. To permit the interior of the food product to be heated through the direct absorption of microwaves, microwave cooking containers are generally transparent to microwave energy. Specifically, the food product is heated since the microwaves cause water molecules within the food product to oscillate at a high frequency and the resulting molecular friction generates heat. In the case where microwaves are utilized to directly heat a high moisture food product, the heating temperature is generally limited to about 100° C. at which point the water content within the food product begins to vaporize. Upon reaching vaporization, the water molecules will move through the food product and disburse in the ambient atmosphere where a portion condenses on the surface of the food product. Undesirably, this process precludes browning or crisping of the food product as it is being heated and, furthermore, may make the food product soggy.
For the purpose of elevating the heating temperature above 100° C., it is also well known in the art to provide microwave cooking containers with a microwave energy absorbing material, commonly referred to as a susceptor. Commonly, susceptors are located in the lower end of the container containing the food product and function to heat the food product by conduction and radiation. By way of example, U.S. Pat. No. 4,553,010 discloses a partially collapsible, microwave food container having a susceptor integrated with the bottom of the food container. Microwave cooking containers having integrated susceptors are not, however, wholly satisfactory since the heat generated by susceptors may present a safety hazard to users, particularly when a user is withdrawing the heated food product container from the microwave oven. Furthermore, integrated susceptors may radiate heat unevenly resulting in hot spots that can cause the container and/or the food product to overheat. Overheating of the food product is undesirable as it tends to dry-out and/or overcook the food product.
To provide for the popping of popcorn in a microwave oven, it is further known to provide a microwave cooking container that comprises a bag or pouch containing un-popped popcorn and hydrogenated cooking fat. In addition, the bag or pouch has a susceptor integrated into its bottom that becomes heated as it absorbs microwave radiation. In this manner, the susceptor and the direct microwave energy cooperate to pop the popcorn as the susceptor conducts heat upwardly into the popcorn kernels while water stored in the kernels is caused to vaporize until such time as the internal pressure is sufficient to explosively rupture the outer shell or pericarp of the popcorn kernel. The bag or pouch is constructed to permit expansion under the influence of the internal vapor pressure to accommodate the increase in volume as the popcorn pops.
Still further, it is known to provide a microwave cooking container that comprises a collapsible box for use in popping popcorn. By way of additional example, U.S. Pat. No. 5,486,939 discloses a collapsible box formed of a cardboard material where the side walls are collapsible when pressure is applied to the bottom and top walls. The collapsible box is expandable to define an interior heating space when pressure is applied to a junction of a rear wall and one of the top and bottom walls and a junction of a front wall and the other of the top and bottom walls. This disclosed, collapsible box further includes a susceptor that is disposed on the bottom wall and on a strip at the lower edges of the front, rear, and side walls. Inside the collapsible container is a quantity of cooking oil, salt, and un-popped popcorn.
Even more recently, a collapsible box incorporating a susceptor pouch has been developed, in which the collapsible box employs a “susceptor pouch,” as opposed to a susceptor integrated with the box walls. The use of a separate susceptor pouch, which is not integrated into the box walls, provides flexibility in manufacturing and shipping as well as avoiding some of the problems mentioned above. However, this container also has its drawbacks. Particularly, this container could be very hot to the touch after cooking, has a tendency to leak through the bottom corners of the box, and does not satisfactorily “lock” into its expanded configuration.
While the aforementioned microwave cooking containers generally work for their intended purpose, they have not addressed the need for an improved, collapsible microwave cooking container that is relatively economical to manufacture, i.e., a container that eliminates the need and costs associated with providing extra leak containing elements. A need also remains for a collapsible microwave cooking container that has improved “locking” characteristics for use during the expansion process. A still further need remains for a collapsible microwave cooking container having a means for allowing the heated container to be more easily removed from the microwave oven. Yet another need exists for a collapsible microwave cooking container which minimizes venting to, in turn, optimize pop volume of to-be-cooked popcorn.
These and other objects of the invention are addressed in the specification, claims and drawings of the present application.